KUALA LUMPUR (AFP) - United States President Barack Obama, who on Saturday became the first sitting US president in nearly 50 years to visit moderate-Muslim Malaysia, said both the US and Malaysia can draw strength from ethnic and religious diversity.

"While we may be different as nations, our people have similar hopes and similar aspirations," Mr Obama said in a toast to Malaysia's King, Sultan Abdul Halim Mu'adzam Shah, at a state dinner. "We can draw strength in both our nations from our ethnic and religious diversity."

He also quickly expressed solidarity with his hosts over the mystery of missing Malaysia Airlines flight MH370.

US ties with economically successful, Malaysia have vastly improved after years of anti-US antagonism under former leader Mahathir Mohamad.

Washington sees Malaysia as a pivotal player in South-east Asia, and talks with Prime Minister Najib Razak will concentrate on increasing convergence in trade, security cooperation and intelligence-sharing.

Mr Obama touched down on the third leg of a four-nation Asia tour designed to showcase his "rebalance" of US resources to the dynamic region, but which has been repeatedly interrupted by foreign policy crises from Ukraine to the Middle East.

He also arrived on what is his first-ever visit to Malaysia with the country under uncomfortable scrutiny over its handling of tragedy over the airliner which vanished on March 8 with 239 people aboard.

Transport Minister Hishammuddin Hussein said Mr Obama told him he knows "it is a tough, long, road ahead".

"We'll work together. There is always support," Mr Hishammuddin said the US leader told him at a humid arrival ceremony under grey skies punctuated with a crashing formal field gun salute.

"I'm very happy to hear (this) because it is a long journey."

Mr Obama's tour reaffirms his view that the United States is a key Pacific power in a region where US allies are discomforted by the rise of China and where maritime tensions have disrupted years of relative calm between nations.

Malaysia is among several nations with competing territorial claims in the South China Sea, where Beijing's assertiveness has sparked alarm.

In Japan, Mr Obama made clear that US mutual defence agreements with Tokyo covered disputed islands in the East China Sea also claimed by Beijing.

But in a sign of festering tensions, the Japanese authorities said two Chinese coastguard ships sailed into Japan's territorial waters around the islands again on Saturday - just two days after Mr Obama left Tokyo.

The White House last year rebuked China for setting up what it said was an "illegitimate" air defence identification zone in the East China Sea. On Saturday, Air Force One flew through the zone en route to Malaysia.

In a Malaysian newspaper interview published on Saturday, Mr Obama touted growing security cooperation with Malaysia as a way to ensure "freedom of navigation in critical waterways" and that nations "play by the same rules" - a clear reference to China.

Mr Obama has a professed affinity with South-east Asia, having spent four years as a boy in Indonesia.

He will simultaneously court Datuk Seri Najib and acknowledge rising discontent with the corruption-plagued coalition in power for 57 years, which is accused of persecuting opponents.

"We support an open political process in Malaysia. We have been concerned when we see any restrictions on the political space," said Mr Ben Rhodes, a deputy national security adviser.

The White House skipped a meeting between Mr Obama and opposition leader Anwar Ibrahim, who faces five years in jail on a March 7 sodomy conviction he calls politically motivated and which the US government has criticised.

Mr Anwar will instead meet US national security adviser Susan Rice.

Mr Rhodes said Mr Obama will discuss the broader issue of political freedoms in a town hall speech to South-east Asian youth leaders on Sunday, and stressed the President does not always meet opposition leaders when overseas.

Mr Obama will however meet representatives of civil-society groups critical of Mr Najib's government.

The President is also expected to try to ease Malaysian concerns on his stalled plans for a 12 nation Trans-Pacific trade agreement, which has been delayed by tough negotiations among potential partners.